From Bavarian Autosport Code Reader:
C6 - Cat Efficiency Cyl #1 - 3
E3 - Oxy Sensor Adaption Limit #1 - 3
E4 - Oxy Sensor Adaption Limit Cyl #4 - 6
BD - Pre Cat Oxy Sensor Heater Circuit #4 - 6
I replaced Oxy Sensors about 30,000 miles ago, but they were cheap ones.
I hate to say how old the plugs are; more than 30,000.
No recent maintenance regarding these issues. But E3 and E 4 have always been an issue.
197,000 Total miles
Thanks!